1. Field of the Invention
The present invention relates to an illuminator that illuminates an object, such as a picture, a poster, a sculpture, or the like, which is capable of showing particular colors in response to ultraviolet light.
2. Description of the Related Art
Recently, a coating material is produced which emits or reflects white visible light within a predetermined wavelength region in response to irradiation of ultraviolet light. When an object for appreciation, such as a picture, a poster, a sculpture, or the like, is coated with the coating material, and irradiated with ultraviolet light, colors different from original colors of the object are caused to appear so as to cause the object to emerge in a varied status before an appreciator or a viewer.
Further, there has been proposed an illuminator configured such that the white visible light and ultraviolet light are repeatedly and periodically turned on and off in order to cause the object to alternately appear in a state for appreciation, as described above, wherein the colors of the object are changed by using ultraviolet light as a light source, and in an original state by irradiation with white light, thereby realizing a state of irradiation of an object with either of white visible light and ultraviolet light and/or a state of irradiation of the same with both of them.
The proposed illuminator constructed as above is usually configured to employ filaments that emit thermoelectrons, for light sources for ultraviolet light and the white visible light. However, due to the periodic supply of the electric power to the filaments for the purpose of the periodic irradiation described above, metal of the filaments is repeatedly vaporized and restored to its original state, which causes each filament to undergo a change in the multilayer metal structure thereof, so that the service life of the filament is inevitably shortened.
However, there has never been proposed any illuminator that provides an improvement in the service life of discharge tubes over the above-described conventional illuminator.